The present invention relates in general to the art of earth boring and, more particularly, to an improved cutting structure for a milled tooth rotary rock bit. A type of rotary rock bit used for drilling earth boreholes for the exploration and production of oil and gas and the likes is commonly known as a milled tooth bit. This type of bit employs a multiplicity of rolling cone cutters rotatably mounted on bearing pins extending from the arms of the bit. The cutters are mounted on axes which extend downwardly and inwardly with respect to the bit axis so that the conical sides of the cutters tend to roll on the bottom of the hole and contact the formations. The rolling cone cutters have circumferential rows of teeth to drill the formations at the bottom of the hole. The rows of teeth on each cutter are often located in offset relation to the corresponding rows on the other cutters and drill separate tracks at the bottom of the hole. The teeth tend to wear in a vertical direction and along the ends which engage the peripheral wall of the hole during the drilling operation.
The service life of the tooth cutting structure may be improved by the addition of tungsten carbide particles to certain wear areas of the teeth. This operation is known as "hardfacing". The hardfacing may be designed to create a wear or erosion pattern to produce a self-sharpening tooth profile. The severe use which milled tooth bits encounter results in the components of the bit being repeatedly subjected to much higher stresses with respect to the ultimate strength of the material, than is commonly encountered in other types of machines. In addition, the bits must function profitably in different earth formations. The geometry of the bit must provide a well balanced cutting structure. The efficient use of available space is extremely important. The relationship between the cutters is such that a change in the shape or size of any one cutter affects the other cutters. The determination of cone shape or cone contour is critical.